William F. Ruddiman pose an interesting hypothesis by arguing that humans have had a measurable impact on the climate system for 8000 years. In his book “Plow, Plagues and Petroleum”, the emeritus environmental science professor shows interesting anomalies in the trends of atmospheric CO2 concentration (since 8000 years) ago when Europeans start cutting down forest in Middle and Eastern Europe for agriculture, and CH4 concentration (since 5000 years) when irrigated rice farming started at large scale. This has led to an temperature increase of 0.8 degrees Celsius before the industrial revolution started which led to a similar amount of emissions, but in a much shorter period. Ruddiman argues that instead of heading to a cooler climate, as was expected from traditional climatology (due to regular orbital changes) increased human-induced emissions avoided this cooling down, and may lead to a brief warming period (on geological scale). There is also an interesting chapter where brief declines of CO2 concentrations are related to major pandamics (like black plague), which led to a temporarely regrowth of forests. If Ruddiman’s thesis is true humans have unconsiously entended the K-phase of preferable climate before a dramatic reorganization phase (in the coming years?) occur.